Apparatus for electrolytically tuning an end wire fixture



May 22, 1956 w. E. WHITTINGTON APPARATUS FOR ELECTROLYTICALLY TUNING AN END WIRE FIXTURE 2 Sheets-Sheet 1 Filed Feb. 13, 1955 INVENTOR. Mill/9M1: MV/TI/A/GTO/V A? r ORA/I) May 22, 1956 w E. WHITTINGTON 2,746,918

APPARATUS FOR ELECTROLYTICALLY TUNING AN END WIRE FIXTURE 2 Sheets-Sheet 2 Filed Feb. 13, 1955 INVENTOR. mil/AM Z: MII'f/A/GTON Afro/PAM? United States Patent APPARATUS FOR ELECTROLYTICALLY TUNENG AN END WIRE FIXTURE William E. Whittington, North Hollywood, Calif., assignor to Collins Radio Company, Cedar Rapids, Iowa, a cor poration of Iowa Application February 13, 1953, Serial No. 336,677 2 Claims. (Cl. 204-422) This invention relates in general to means for accurately tuning an end wire section of an electromechanical filter.

Electromechanical filters, such as described in co-pending applications No. 248,011, filed September 24, 1951, and No. 283,340, filed April 21, 1952, comprise a plurality of discs which are connected together by longitudinal supporting wires and which have end discs that are connected to driving wires.

The discs are tuned to a resonant frequency, and it has been discovered that the end wires must also be tuned to the resonant frequency so as to obtain a composite filter which operates most efiiciently.

It is an object of this invention, therefore, to provide a tuning fixture and method wherein a dimension of a vi bratory element may be adjusted until the desired frequency response is obtained.

Another object of this invention curately the tuning of an end Wire.

Further features, objects and advantages of this invention will become apparent from the following description and claims when read in view of the drawings, in which:

Figure 1 is a perspective view of the end tuning fixture of this invention;

Figure 2 is an elevational view of ture;

Figure 3 is an enlarged sectional view of the top of the U-shaped tube;

Figure 4 is an enlarged sectional view of the pick-up and driving coils; and,

Figure 5 is a frequency versus voltage response curve.

This invention allows the length of end driving wires to be varied until they are resonant at a desired frequency. Electrolysis is used to vary the length of an end wire un til the desired frequency is obtained.

Figure 1 illustrates a base plate upon which is mounted a first upright post 11 that has a bracket 12 attached thereto which supports a container 13.

The container or receptacle 13 has a U-shaped tube 14 attached to its bottom. Above the bracket 12 on the first upright 11 is a second supporting bracket 16 which extends outward and above the container 13. The bracket 16 is formed with a threaded opening 17 through which a threaded shaft 18 is received. A knob 19 is connected to the upper end of shaft 18 and a plunger 21 is attached to the lower end and received in the container 13. The plunger 21 is made of electrical insulating material as, for example, a non-conducting plastic or glass.

A second upright member 22 is attached to the base 19 and a slidable bracket 23 is mounted thereon and is formed with a pair of openings 24 and 25. The first opening 24 is receivable over a third upright member 26 mounted on the frame 10, and the second opening 25 receives member 22 therethrough. The member 22 is shorter than the post 26 to allow the bracket to pivot about member 26. Member 22, therefore, serves as a guide for the bracket. The upper end 27 of post 26 is enlarged so that the bracket 23 cannot be removed. A second holding is to control very acthe end tuning fix- 2,746,918 Patented May 22, 1956 2 bracket 15 is mounted to upright member 22 and supports tube 14.

A filter supporting portion 28 is attached to the end of the bracket 23 and a filter assembly 29 is received therein. The filter assembly has a cylinder 31 attached to each end through which driving wires 32 extend. A plurality of discs 33 are mounted between cylinders 31 by coupling wires 34. The driving wires 32 are connected to the end discs of the filter assembly. A third opening 36 is formed through the bracket 23 and one of the cylinders 31 is received therein and clamped by a set screw 37. For a more detailed description of the filter assembly 29, ref erence may be made to the co-pending applications Ser. No. 248,011, filed September 24, 1951, and Ser. No. 283,340, filed April 21, 1952.

The second end 33 of the U-shaped tube 14 is small enough to fit inside the cylinder 31 and receive the end of the driving wire 32 therein as shown in Figure 4.

An electrical conducting liquid, as for example, a salt solution of sodium chloride in water is contained in the container 13 and the U-shaped tube 14, and the level of the liquid in the tube may be adjusted by moving plunger 21.

A direct current source 39 is connected by leads 41 and to a pair of terminals 43 and 44 mounted on the frame. The terminal 53 is connected electrically to the frame 10 which is an electrical conductor and the other terminal is insulated from the frame and connected by a lead to an electrode 47 that is inserted into the container 13. Since the upright member 26, the bracket 23, and the cylinder 31 are electrical conductors, a circuit will be completed from the electrode 47 through the liquid to the driving wire 32 mounted in the liquid. It is to be realized, of course, that the tube 14 is made of a non-conducting material, as for example, glass.

Pick-up coil 49 is supported about the end 33 of the tube by an adapter cylinder 51. A drive coil 52 is also supported within the adapter cylinder as shown in Figure 4. The adapter cylinder is received over the end 38 of the tube and has an aligning shoulder 53 which engages an enlarged portion 54 of the tube. The upper end of the adapter 51 fits into the cylinder 31. The pick-up coil 49 is connected by leads 56 and 57 to an oscilloscope 58 and the drive coil 52 is connected by leads 59 and 69 to a variable oscillator 61. At times it may be desirable to place coils d= and 52 above the end of tube 38 so that closer coupling may occur. This may be accomplished by reducing the length of the tube and decreasing the diameter of the coils.

in operation a filter assembly 29 is inserted in the pot- 23 the set screw 37 is tightened on the cylinder 31 to hold it in a predetermined position. This is done in the osition shown in Figure 2 so that the end wire 32 of the lter will be aligned by a funnel-shaped member 62 mountthe plate 19. The bracket 23 is then pivoted about the shaft 2 the third upright 22 is received through the opening 25.

The e..d wit is received in the tube 33 as shown in Figure Th plunger 21 is adjusted by knob 19 until the end wire 32 is received within the liquid. The oscillator 51 will feed an electrical input into the coil 52 which will couple energy to the driving wire 32, and the pickup coil will indicate the amplitude of the vibrations.

The voltage source 39 will be connected and the end wire 32 will be shortened due to electrolytic action. This varies the resonant frequency of the wire because the length of the wire affects frequency. When the desired frequency is indicated by the oscilloscope 58, the voltage source 39 is then disconnected and the filter removed therefrom.

The output of the oscillator 61 may be swept over a range of frequencies and the oscilloscope will give a presentation such as shown in Figure 5. The dip in the curve is due'toabsorption of energy by thediscs of'the'filter assembly and thus indicates the resonant frequency of the end wires 32. When this dip is symmetrical in the curve, the end wire is correctly tuned; The end wire will then be tuned to the desired frequency.

The otherendlwire 32 may then be tunedby loosening the set screw 37 and inserting the other cylinder 31 into the holding portion 28 and the procedure will be repeated. Then the filter assembly will be completely tuned and ready for final assembly in its case,

It is seen that this invention provides means for very accurately tuning end wires of an electromechanical filter.

Although the invention has been described with respect to particular embodiments thereof, it is not to be so limited as changes and modifications may be made, therein which are within the full intended scope of the invention, as defined by the appended claims.

I claim:

1. lv'leans for electrolytically tuningan end wire fixture comprising, abase plate, a first upright mounted on said base plate, a first holding bracket attached to said first upright, acontainer having an open top supported by said first bracket, a U tube connected at one end to the bottom ot said container and communicating therewith, the other end extending substantially to the top of the container and outside thereof, said container and said U tube adapted to contain a liquid electrolyte, a second bracket supported on said first upright, a plunger threadedly received through said second bracket and extending into said container, at second upright member mounted on said base plate, a third bracket supported on. said second upright member adapted to support a filter assembly with an end wire extending into the confines of said U tube at 4 said other end, means for applying a direct current potential 'between'said' end wireand'said electrolyte so as to cause electrolytic action on said end wire, a driving coil mounted adjacent said other end of said U tube, a variable frequency oscillator connected to said driving coil, a pickup coil mounted adjacent said other end of said U tube, and an indicating means attached to said pick-up coil to indicate the resonant frequency of said filter assembly.

2. Means for shortening an end wire so'as to tune it by electrolytic action comprising, a base plate, a U tube mounted upright onsaid base plate with one end enlarged and the other end decreased in size, adapted to contain a liquid electrolyte, means for varying the level of said electrolyte, support means adjacent thesmall end of said U tube adapted to support a filter assembly having an end wire with said end wire extending into the small end of said U tube, driving and pick-up coils mounted adjacent the small end of said U tube, said driving coil connected to a variable frequency oscillator, said pick-up coil connected to an indicating means, and means for supplyinga direct current potential between said electrolyte and said endwire.

References Cited in the'file of this patent UNITED STATES PATENTS' 1,298,155 Anthony Mar. 25, 1919 1,738,801 Shemitz Dec. 10, 1929 2,364,501 Wolfskill Dec. 5, 1944 2,411,298 Shorev Nov. 19, 1946 2,434,286 Pfann Jan. 13, 1948 2,690,803 Wallace Oct. 5, 1954 FOREIGN PATENT S 373,398 Germany Apr. 12, 1923 

1. MEANS FOR ELECTROLYTICALLY TUNING AN END WIRE FIXTURE COMPRISING, A BASE PLATE, A FIRST UPRIGHT MOUNTED ON SAID BASE PLATE, A FIRST HOLDING BRACKET ATTACHED TO SAID FIRST UPRIGHT, A CONTAINER HAVING AN OPEN TOP SUPPORTED BY SAID FIRST BRACKET, A U TUBE CONNECTED AT ONE END TO THE BOTTOM OF SAID CONTAINER AND COMMUNICATING THEREWITH, THE OTHER END EXTENDING SUBSTANTIALLY TO THE TOP OF THE CONTAINER AND OUTSIDE THEREOF, SAID CONTAINER AND SAID U TUBE ADAPTED TO CONTAIN A LIQUID ELECTROLYTE, A SECOND BRACKET SUPPORTED ON SAID FIRST UPRIGHT, A PLUNGER THREADEDLY RECEIVED THROUGH SAID SECOND BRACKET AND EXTENDING INTO SAID CONTAINER, A SECOND UPRIGHT MEMBER MOUNTED ON SAID BASE PLATE, A THIRD BRACKET SUPPORTED ON SAID SECOND UPRIGHT MEMBER ADAPTED TO SUPPORT A FILTER ASSEMBLY WITH AN END WIRE EXTENDING INTO THE CONFINES OF SAID U TUBE AT SAID OTHER END, MEANS FOR APPLYING A DIRECT CURRENT POTENTIAL BETWEEN SAID END WIRE AND SAID ELECTROLYTE SO AS TO CAUSE ELECTROLYTIC ACTION ON SAID END WIRE, A DRIVING COIL MOUNTED ADJACENT SAID OTHER END OF SAID U TUBE, A VARIABLE FREQUENCY OSCILLATOR CONNECTED TO SAID DRIVING COIL, A PICKUP COIL MOUNTED ADJACENT SAID OTHER END OF SAID U TUBE, AND AN INDICATING MEANS ATTACHED TO SAID PICK-UP COIL TO INDICATE THE RESONANT FREQUENCY OF SAID FILTER ASSEMBLY. 